Supported catalyst, preparation method thereof and method for synthesizing allyl acetate by using supported catalyst

Abstract

The invention belongs to the technical field of synthesis of propylene acetate, and discloses a supported catalyst, a preparation method thereof and a method for synthesizing propylene acetate by using the supported catalyst. The preparation method comprises the following steps: mixing and dispersing a metal palladium source, a metal copper source, a polymer stabilizer and a solvent to prepare a metal precursor solution; after a carrier is treated with alkali liquor, a metal precursor solution is sprayed to the surface of the carrier; then carrying out reduction treatment under the action of a reducing agent; and finally, dipping by adopting an acetate solution to prepare the supported catalyst. The polymer stabilizer is selected from at least one of polyvinyl alcohol, polyimide, carboxymethyl cellulose sodium, polyethyleneimine, polyacrylic acid and polymethyl methacrylate. The supported catalyst for synthesizing allyl acetate provided by the invention has high catalyst activity, can improve the utilization rate of noble metals, the conversion rate of reactants and the selectivity of reaction products, and reduces the synthesis cost of allyl acetate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of propylene acetate synthesis, and particularly relates to a supported catalyst, a preparation method thereof and a method for synthesizing propylene acetate by using the same. BACKGROUND

[0002] Propylene acetate is an important organic chemical raw material and intermediate. For example, propylene acetate can be used to produce propylene alcohol through a hydrolysis reaction. Propylene alcohol is an important raw material for synthesizing glycerol, medicines, spices and resins. Propylene acetate can be used to prepare acrylic acid or its esters (such as methyl acrylate) through a chemical reaction, which are important monomers for producing acrylic resin, plastic, paint, adhesive and the like. Organic synthesis intermediate: by using its double bond and ester group, it can be used as a starting material for synthesizing various fine chemicals (such as medicines, pesticides and spices).

[0003] At present, the main route for generating propylene acetate is a catalytic oxidation method, that is, propylene, oxygen and acetic acid are used as raw materials to perform a gas phase reaction in a fixed bed reactor under the action of a catalyst. Early research mainly obtained a uniform catalyst through an impregnation method, but the utilization rate and activity of noble metals were very low. For example, a catalyst is prepared by loading a palladium metal active component and an alkali (earth) metal additive on a silica carrier, but the catalyst has low activity, the space-time yield is not more than 60 g / h / L of catalyst, and the selectivity is only 87%, and there are many by-products. There is also a catalyst using palladium as a main catalyst and copper as an auxiliary catalyst, and similarly, the catalytic activity and selectivity of the catalyst are not high.

[0004] Therefore, it is of great significance to develop a propylene acetate catalyst with high catalytic activity and high selectivity and capable of improving the utilization rate of noble metals for the development of the propylene acetate industry. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a supported catalyst, a preparation method thereof and a method for synthesizing propylene acetate by using the same. The supported catalyst provided by the present application has high catalytic activity, can improve the utilization rate of noble metals, the conversion rate of reactants and the selectivity of reaction products, and reduces the cost of synthesizing propylene acetate.

[0006] The present application provides a preparation method of a supported catalyst.

[0007] Specifically, the preparation method of the supported catalyst comprises the following steps: The metal palladium source, the metal copper source, the polymer stabilizer and the solvent are mixed and dispersed to prepare a metal precursor solution; the carrier is treated with lye, the metal precursor solution is sprayed on the surface of the carrier, and the catalyst precursor is obtained after standing and drying; then the catalyst precursor is reduced by a reducing agent; finally, after drying, an acetate solution is used for impregnation to obtain a supported catalyst; The polymer stabilizer is at least one of polyvinyl alcohol, polyimide, sodium hydroxymethyl cellulose, polyethyleneimine, polyacrylic acid and polymethyl methacrylate.

[0008] Preferably, the molecular weight of the polymer stabilizer is 10000-200000; further preferably, the molecular weight of the polymer stabilizer is 50000-100000, such as 50000-70000.

[0009] Preferably, the metal palladium source is one or more of chloropalladic acid, palladium chloride, palladium nitrate, palladium acetylacetone, potassium tetrachloropalladate.

[0010] Preferably, the mass of metal palladium in the metal palladium source accounts for 0.1%-5% of the mass of the carrier; further preferably, the mass of metal palladium in the metal palladium source accounts for 0.3%-1.5%, such as 0.6%-1.0% of the mass of the carrier.

[0011] Preferably, the metal copper source is one or more of copper chloride, copper sulfate, copper acetate, copper acetylacetone and copper nitrate.

[0012] Preferably, the mass of metal copper in the metal copper source accounts for 0.01%-0.5% of the mass of the carrier; further preferably, the mass of metal copper in the metal copper source accounts for 0.03%-0.15%, such as 0.06%-0.1% of the mass of the carrier.

[0013] Preferably, the mass of metal palladium in the metal palladium source is 5-12 times the mass of metal copper in the metal copper source; further preferably, the mass of metal palladium in the metal palladium source is 8-10 times the mass of metal copper in the metal copper source.

[0014] It should be understood that the process of preparing the metal precursor solution has no special requirements, which can ensure that the metal palladium source and the metal copper source can be uniformly dispersed in the solvent, and the polymer stabilizer can uniformly coat the surface of the metal palladium source and the metal copper source to form a uniform and stable metal precursor solution. In some embodiments of the present application, the process of preparing the metal precursor solution is as follows: the metal palladium source and the metal copper source are added to the solvent and ultrasonic dispersion treatment is performed for 30-60 min; then the polymer stabilizer is added, stirred, and ultrasonic dispersion treatment is performed again for 30-60 min to obtain the metal precursor solution.

[0015] Preferably, the solvent is water, and the amount of water used is 95%-105% of the water absorption capacity of the carrier.

[0016] Preferably, the carrier is selected from one or more of silica, alumina, diatomite, and cordierite.

[0017] Preferably, the carrier is a sphere with a diameter of 3-8 mm, and the average pore size of the carrier is 10-100 nm, and the pore size distribution is 10-100 nm; further preferably, the average pore size of the carrier is 20-50 nm, and the pore size distribution is 20-40 nm.

[0018] Preferably, the alkali solution is a solution formed by at least one of sodium silicate, potassium silicate, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, and potassium phosphate.

[0019] Preferably, the process of alkali solution treatment is to immerse the carrier in the alkali solution in an equal volume for 1-3 hours. The amount of alkali solution is slightly greater than the amount of metal palladium in the metal palladium source and the amount of metal copper in the metal copper source, so as to ensure that the metal palladium and the metal copper can completely form a precipitate. The step of alkali solution treatment further comprises a drying step.

[0020] Preferably, the process of standing is to stand at room temperature (15-30°C) for 10-36 hours.

[0021] Preferably, the reducing agent comprises a liquid phase reducing agent and / or a gas phase reducing agent, the liquid phase reducing agent comprises at least one of hydrazine hydrate, sodium borohydride, potassium borohydride, formaldehyde, ethylene glycol, glucose, sodium hypophosphite, and sodium formate; and the gas phase reducing agent is selected from one of hydrogen gas, hydrogen-nitrogen mixed gas, or hydrogen-argon mixed gas.

[0022] Preferably, the process of washing after the reduction treatment further comprises a washing process, and the washing process is to use deionized water for washing until the conductivity of the washing liquid is less than 50 us / cm.

[0023] Preferably, the acetate solution comprises, but is not limited to, a potassium acetate solution.

[0024] The application further provides a supported catalyst.

[0025] In particular, a supported catalyst is prepared by the above preparation method.

[0026] The application further provides a synthesis method of propylene acetate.

[0027] In particular, a synthesis method of propylene acetate is used to synthesize propylene acetate by using the above supported catalyst, and comprises the following steps: Propylene, nitrogen, acetic acid and oxygen are introduced into the reaction system in a molar ratio of 1:(0.9-1.2):(0.2-0.3):(0.1-0.2) under the action of the above supported catalyst to produce propylene acetate; the reaction temperature is 140-180℃, the reaction pressure is 0.4-1.0 Mpa, and the raw material volume space velocity is 1500-3000 h -1 .

[0028] Compared with the prior art, the present application has the following advantages: The present application introduces a specific polymer stabilizer into the metal precursor solution, combines the spray loading mode and controls the timing of the lye impregnation, and thus a supported catalyst with higher catalytic activity and higher utilization rate of noble metal is prepared. The introduction of the specific polymer stabilizer improves the dispersion effect of the active components (metallic palladium and metallic copper), is more suitable for the spray loading mode, and is combined with the process of first lye impregnation and then spray coating, so that the active components can be better loaded on the outer surface of the carrier, which is beneficial to the synthesis reaction of propylene acetate. The supported catalyst for synthesizing propylene acetate provided by the present application has high catalyst activity, can improve the utilization rate of noble metal, the conversion rate of reactants and the selectivity of reaction products, and reduces the cost of propylene acetate synthesis. DETAILED DESCRIPTION

[0029] In order to make those skilled in the art more clearly understand the technical solutions described in the present application, the following examples are provided for illustration. It should be pointed out that the following examples do not constitute a limitation on the scope of protection required by the present application.

[0030] Unless otherwise specified, the raw materials, reagents or devices used in the following examples and comparative examples can be obtained from conventional commercial channels or can be obtained by known methods.

[0031] Example 1 A preparation method of a supported catalyst, comprising the following steps: A metal precursor solution was prepared by adding 5 g of polyvinyl alcohol with a molecular weight of 10000 to 50 mL (equivalent to 90% of the water absorption capacity of the carrier) of an aqueous solution containing 1.942 g of sodium tetrachloropalladate (containing 0.7 g of palladium) and 0.148 g of copper chloride (containing 0.07 g of copper), and fully dissolving to obtain a metal precursor solution for standby.

[0032] A lye-treated silica carrier was obtained by adding 100 g of a silica carrier (spheres with a diameter of 5 mm, an average pore size of 30 nm, and a pore size distribution of 20-40 nm) to 50 mL of an aqueous solution containing 0.369 g of sodium hydroxide, fully impregnating the carrier with the aqueous solution, and drying.

[0033] The metal precursor solution was uniformly sprayed on the alkali-treated silica carrier, and left at room temperature (25°C) for 20 h to obtain a catalyst precursor. Then, a sufficient amount of hydrazine hydrate was added for reduction treatment. After the reduction treatment, the catalyst was washed with deionized water until the conductivity of the filtrate was less than 50 us / cm; after drying at 110°C, the catalyst was fully immersed in 50 mL of an aqueous solution containing 11.295 g of potassium acetate, and finally dried in an oven at 110°C for 20 h to obtain a supported catalyst.

[0034] Example 2 A method for preparing a supported catalyst, comprising the following steps: In 50 mL (equivalent to 90% of the water absorption amount of the carrier) of an aqueous solution containing 1.942 g of sodium tetrachloropalladate (containing 0.7 g of palladium) and 0.148 g of copper chloride (containing 0.07 g of copper), 5 g of polyvinyl alcohol with a molecular weight of 50,000 was added and fully dissolved to obtain a metal precursor solution, which was ready for use.

[0035] In 50 mL of an aqueous solution containing 0.369 g of sodium hydroxide, 100 g of a silica carrier was added, and the carrier was fully immersed in the aqueous solution and dried to obtain an alkali-treated silica carrier.

[0036] The metal precursor solution was uniformly sprayed on the alkali-treated silica carrier, and left at room temperature (25°C) for 20 h to obtain a catalyst precursor. Then, a sufficient amount of hydrazine hydrate was added for reduction treatment. After the reduction treatment, the catalyst was washed with deionized water until the conductivity of the filtrate was less than 50 us / cm; after drying at 110°C, the catalyst was fully immersed in 50 mL of an aqueous solution containing 11.295 g of potassium acetate, and finally dried in an oven at 110°C for 20 h to obtain a supported catalyst.

[0037] Example 3 A method for preparing a supported catalyst, comprising the following steps: In 50 mL (equivalent to 90% of the water absorption amount of the carrier) of an aqueous solution containing 1.942 g of sodium tetrachloropalladate (containing 0.7 g of palladium) and 0.148 g of copper chloride (containing 0.07 g of copper), 5 g of polyvinyl alcohol with a molecular weight of 50,000 was added and fully dissolved to obtain a metal precursor solution, which was ready for use.

[0038] In 50 mL of an aqueous solution containing 0.369 g of sodium hydroxide, 100 g of a silica carrier was added, and the carrier was fully immersed in the aqueous solution and dried to obtain an alkali-treated silica carrier.

[0039] The metal precursor solution was uniformly sprayed on the alkali-treated silica carrier, and left to stand at room temperature (25°C) for 20 h to obtain a catalyst precursor. Then, a sufficient amount of hydrazine hydrate was added for reduction treatment. After the reduction treatment, the catalyst was washed with deionized water until the conductivity of the filtrate was less than 50 us / cm; then, after drying at 110°C, the catalyst was fully immersed in 50 mL of an aqueous solution containing 11.295 g of potassium acetate, and finally dried in an oven at 110°C for 20 h to obtain a supported catalyst.

[0040] Example 4 A method for preparing a supported catalyst, comprising the following steps: In 50 mL (equivalent to 90% of the water absorption amount of the carrier) of an aqueous solution containing 1.387 g of sodium tetrachloropalladate (containing 0.5 g of palladium) and 0.106 g of copper chloride (containing 0.05 g of copper), 5 g of polyvinyl alcohol with a molecular weight of 50,000 was added and fully dissolved to obtain a metal precursor solution, which was ready for use.

[0041] In 50 mL of an aqueous solution containing 0.369 g of sodium hydroxide, 100 g of a silica carrier was added, and the carrier was fully immersed in the aqueous solution and dried to obtain an alkali-treated silica carrier.

[0042] The metal precursor solution was uniformly sprayed on the alkali-treated silica carrier, and left to stand at room temperature (25°C) for 20 h to obtain a catalyst precursor. Then, a sufficient amount of hydrazine hydrate was added for reduction treatment. After the reduction treatment, the catalyst was washed with deionized water until the conductivity of the filtrate was less than 50 us / cm; then, after drying at 110°C, the catalyst was fully immersed in 50 mL of an aqueous solution containing 11.295 g of potassium acetate, and finally dried in an oven at 110°C for 20 h to obtain a supported catalyst.

[0043] Comparative Example 1 A method for preparing a supported catalyst, comprising the following steps: In 50 mL (equivalent to 90% of the water absorption amount of the carrier) of an aqueous solution containing 1.387 g of sodium tetrachloropalladate (containing 0.5 g of palladium) and 0.106 g of copper chloride (containing 0.05 g of copper), 5 g of polyvinyl alcohol with a molecular weight of 50,000 was added and fully dissolved to obtain a metal precursor solution, which was ready for use.

[0044] Comparative Example 2 A method for preparing a supported catalyst, comprising the following steps: In 50 mL (equivalent to 90% of the water absorption of the carrier) of an aqueous solution containing 1.942 g of sodium tetrachloropalladate (containing 0.7 g of palladium) and 0.148 g of copper chloride (containing 0.07 g of copper), 5 g of polyvinylpyrrolidone with a molecular weight of 10000 is added and dissolved to obtain a metal precursor solution, which is ready for use.

[0045] In 50 mL of an aqueous solution containing 0.369 g of sodium hydroxide, 100 g of a silica carrier is added, the carrier is fully immersed in the aqueous solution, and dried to obtain a base-treated silica carrier.

[0046] The base-treated silica carrier is fully immersed in the metal precursor solution and placed at room temperature (25°C) for 20 h to obtain a catalyst precursor. Then, a sufficient amount of hydrazine hydrate is added for reduction treatment. After reduction treatment, the catalyst is washed with deionized water until the conductivity of the filtrate is less than 50 us / cm; after drying at 110°C, it is fully immersed in 50 mL of an aqueous solution containing 11.295 g of potassium acetate, and finally dried in an oven at 110°C for 20 h to prepare a supported catalyst.

[0047] Comparative Example 3 A method for preparing a supported catalyst, comprising the following steps: In 50 mL (equivalent to 90% of the water absorption of the carrier) of an aqueous solution containing 1.942 g of sodium tetrachloropalladate (containing 0.7 g of palladium) and 0.148 g of copper chloride (containing 0.07 g of copper), 5 g of polyvinylpyrrolidone with a molecular weight of 10000 is added and dissolved to obtain a metal precursor solution, which is ready for use.

[0048] In 50 mL of an aqueous solution containing 0.369 g of sodium hydroxide, 100 g of a silica carrier is added, the carrier is fully immersed in the aqueous solution, and dried to obtain a base-treated silica carrier.

[0049] The base-treated silica carrier is fully immersed in the metal precursor solution and placed at room temperature (25°C) for 20 h to obtain a catalyst precursor. Then, a sufficient amount of hydrazine hydrate is added for reduction treatment. After reduction treatment, the catalyst is washed with deionized water until the conductivity of the filtrate is less than 50 us / cm; after drying at 110°C, it is fully immersed in 50 mL of an aqueous solution containing 11.295 g of potassium acetate, and finally dried in an oven at 110°C for 20 h to prepare a supported catalyst.

[0050] Evaluation of catalyst performance The supported catalyst prepared by the examples 1-4 and the comparative examples 1-3 was used to synthesize propylene acetate. The specific process was as follows: evaluation in a fixed bed reactor, wherein the catalyst loading amount was 500 mL; the reaction raw material composition (in terms of mole percentage) was n(propylene): n(nitrogen): n(acetic acid): n(oxygen) = 41:43:10:6; the reaction temperature was 145℃; the reaction pressure was 0.75 MPa; the reaction space velocity was 2500 h -1 ; the reaction time was 500 h. The content of each component after the reaction was analyzed by gas chromatography, and then the selectivity and the space-time yield were calculated, and the calculation formula of the selectivity and the space-time yield was as follows: Selectivity (S) = n(mol number of propylene acetate) / [n(mol number of propylene acetate) + 1 / 3n(carbon dioxide)]*100%; Space-time yield (STY) = the mass of the reaction generated propylene acetate / (catalyst volume*reaction time) unit (g / L*h).

[0051] The test data is shown in Table 1.

[0052] Table 1 Performance of the catalyst

[0053] From the data in Table 1, it can be seen that the catalytic activity and the selectivity of the reaction product of the supported catalyst prepared by the examples of the present application are obviously higher than those of the comparative examples, the space-time yield (STY) of propylene acetate is greater than 445 g / L*h, and is as high as 487 g / L*h; the selectivity (S) of propylene acetate is not less than 96.5%, and is as high as 97.6%.

[0054] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as the limitation of the patent scope of the present application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing a supported catalyst, characterized by, The method comprises the following steps: a metal precursor solution is prepared by mixing and dispersing a metal palladium source, a metal copper source, a polymer stabilizer and a solvent; the metal precursor solution is sprayed on the surface of the carrier after the carrier is treated with an alkali solution, and then the catalyst precursor is obtained by standing and drying; then the catalyst precursor is reduced by a reducing agent; finally, the supported catalyst is prepared by impregnating the dried catalyst precursor with an acetate solution; the polymer stabilizer is at least one of polyvinyl alcohol, polyimide, sodium hydroxymethyl cellulose, polyethyleneimine, polyacrylic acid and polymethyl methacrylate.

2. The production method according to claim 1, characterized by, The molecular weight of the polymer stabilizer is 10000-200000.

3. The production method according to claim 1 or 2, characterized by, The mass of the metal palladium in the metal palladium source accounts for 0.1%-5% of the mass of the carrier; the mass of the metal copper in the metal copper source accounts for 0.01%-0.5% of the mass of the carrier.

4. The production method according to claim 3, characterized by, The mass of the metal palladium in the metal palladium source is 5-12 times the mass of the metal copper in the metal copper source.

5. The production method according to claim 1 or 2, characterized by, The solvent is water, and the use amount of the water is 95%-105% of the water absorption amount of the carrier.

6. The production method according to claim 5, wherein The carrier is selected from one or more of silica, alumina, diatomite and cordierite; the carrier is a sphere with a diameter of 3-8mm, the average pore size of the carrier is 10-100nm, and the pore size distribution is 10-100nm.

7. The preparation method according to claim 1, characterized in that, The process of the alkali solution treatment is to immerse the carrier in the alkali solution with an equal volume for 1-3 hours.

8. The method of claim 1, wherein, The reducing agent comprises a liquid phase reducing agent and / or a gas phase reducing agent; the liquid phase reducing agent comprises at least one of hydrazine hydrate, sodium borohydride, potassium borohydride, formaldehyde, ethylene glycol, glucose, sodium hypophosphite and sodium formate; the gas phase reducing agent is selected from one of hydrogen, hydrogen-nitrogen mixed gas or hydrogen-argon mixed gas.

9. A supported catalyst characterized in that, The supported catalyst is prepared by the preparation method of any one of claims 1-8.

10. A method for the synthesis of propylene acetate, characterized by, The supported catalyst of claim 9 is used to synthesize acrylate, The method comprises the following steps: The reaction is carried out by introducing propylene, nitrogen, acetic acid and oxygen into the reaction system in a molar ratio of 1:(0.9-1.2):(0.2-0.3):(0.1-0.2) under the action of the supported catalyst of claim 9, to produce propylene acetate; the reaction temperature is 140-180℃, the reaction pressure is 0.4-1.0 MPa, the raw material volume space velocity is 1500-3000 h -1 .

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